Active water influx into a gas reservoir reduces ultimate recovery from that which would be expected under volumetric conditions due to reduced sweep efficiency and residual gas which is trapped at high pressure. Previous investigations on Gulf Coast gas fields presented in the literature1,2  have demonstrated reservoir management techniques which can increase the expected ultimate recovery over 10% of the original gas in place. This paper presents new work in the form of a detailed case history which extends this emerging technology into aquifer gas storage reservoirs. By their nature, aquifer gas storage fields are water-drive reservoirs. Thus, prudent reservoir management is required to reduce the detrimental effects of trapped gas and poor volumetric sweep.

A detailed reservoir characterization and numerical simulation study are presented for a mid-continent aquifer gas storage field. It is demonstrated that rate optimization during both injection and withdrawal cycles can significantly improve the performance of the storage reservoir. Performance improvements are realized in the form of a larger working volume of gas, a reduced cushion volume of gas, and a decrease in field water production. This research has significant implications for the business facet of the natural gas industry. By utilizing these reservoir management techniques, gas storage operators will be able to minimize their base gas requirements, improve their economics, and determine whether the best use for a particular storage field is base loading or for meeting peak day requirements.

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